Since the day we were told that bacon topped the list of most cancer-causing substances ever, we’ve all been, well, a tad sad. It seems that everything we touch, see or smell lately has the potential to give us cancer. And today, you can add citrus-scented candles to the list too.

And not just candles, even cleaning products or anything that contains the chemical limonene.

Researchers from BBC’s “Trust Me, I’m A Doctor”, working alongside chemistry professor, Alastair Lewis, have been investigating the potential hazards associated with lemon-scented aromas. This is what they found.

For the study, the air in six homes throughout York, England were sampled over a five day period, looking at a number of volatile organic chemicals (VOCs). Each of these samples were tested, and what they found was that the VOC that spiked was limonene – the scent that is often used in candles and cleaning products to give it that lemony, fresh smell.

For every two molecules of limonene released into the air from either a candle or cleaning product, one molecule of formaldehyde was formed – not good. In fact, three of the houses that often used these products had such high levels of limonene, the researchers had to adjust their test so they could retrieve the best possible results from the full range of chemicals.

What you need to know, is that limonene is fairly safe when it’s blended with other chemicals that you could find in candles and cleaning products, but it’s pretty dangerous to inhale solo. However, when it mixes with other airborne elements in your house, limonene modifies and becomes formaldehyde. This is a chemical that is often used to preserve products, but can is also known to be a carcinogen that burns the eyes, irritates the skin, and is said to be linked to nose and throat cancers.

The next stage to the study was to find products that helped reduce the levels of formaldehyde in the air. They found that lavender, spider ferns, guava, grub ferns, squirrel’s foot ferns, and Japanese royal ferns were the most effective at reducing these chemicals in the air. Aside from this, the researchers also recommend limiting the amount of limonene-infused products and in doing so, suggest looking for limonene on the back of the product and opting for a different product if found to be listed. Fragrance-free is always a good option.